A detailed study is being made of the composition and metabolism of testicular lipids of humans of all ages. Tissues are obtained either at surgery or at autopsy. Quantitative analyses of lipic classes and of individual fatty acids are done, using thin-layer, column and gas chromatography. The biosynthesis of fatty acids is studied in tissue homogenates and in sub-cellular fractions incubated with C14 substrates, such as acetate, glucose or citrate. Interconversions and bio-oxidation of long chain saturated and unsaturated fatty acids are being studied. Findings of lipid composition and metabolism are supplemented with histological studies of the tissues in order to relate the chemical and biochemical findings to the structure and physiological functions of this organ. BIBLIOGRAPHIC REFERENCES: Coniglio, J. G., Grogan, W.M., Jr., and Rhamy, R. K., Lipid and Fatty Acid Composition of Human Testes Removed at Autopsy, Biology of Reproduction 12: 255 (1975). Trombly, W.,Tappel, A.L., Coniglio, J. G., Grogan, W. M., Jr. and Rhamy, R. K., Fluorescent Products and Polyunsaturated Fatty Acids of Human Testes. Lipids 10: 591 (1975).